Quantitative contraction rates for Markov chains on general state spaces

We investigate the problem of quantifying contraction coefficients of Markov transition kernels in Kantorovich ($L^1$ Wasserstein) distances. For diffusion processes, relatively precise quantitative bounds on contraction rates have recently been derived by combining appropriate couplings with carefully designed Kantorovich distances. In this paper, we partially carry over this approach from diffusions to Markov chains. We derive quantitative lower bounds on contraction rates for Markov chains on general state spaces that are powerful if the dynamics is dominated by small local moves. For Markov chains on $\mathbb{R^d}$ with isotropic transition kernels, the general bounds can be used efficiently together with a coupling that combines maximal and reflection coupling. The results are applied to Euler discretizations of stochastic differential equations with non-globally contractive drifts, and to the Metropolis adjusted Langevin algorithm for sampling from a class of probability measures on high dimensional state spaces that are not globally log-concave.Comment: 39 page

Pathophysiologie des Kapnoperitoneums: Implikationen für Beatmung und Hämodynamik

Zusammenfassung: Die laparoskopische Chirurgie wurde Anfang der 50er Jahre für gynäkologische Eingriffe eingeführt. Mit verbesserter Technik erweiterte sich das Spektrum in den letzten Jahrzehnten beträchtlich. Es wurden zunehmend komplexere und länger dauernde Operationen durchgeführt. Als Vorteile gegenüber offener Chirurgie wurden eine Reduktion der postoperativen Schmerzen, bessere kosmetische Ergebnisse, raschere Erholung und die Verkürzung der Krankenhausverweildauer angeführt. Infolgedessen wird die Laparoskopie mittlerweile auch bei immer älteren Patienten mit entsprechenden pulmonalen sowie kardiovaskulären Komorbiditäten und in der Chirurgie für adipöse Patienten eingesetzt. Eine sichere Anästhesieführung setzt detaillierte Kenntnisse der Pathophysiologie des Kapnoperitoneums voraus, insbesondere im Hinblick auf dessen respiratorische und hämodynamische Konsequenzen. Der Übersichtsartikel diskutiert die wichtigsten Effekte des Kapnoperitoneums und stellt aktuelle Forschungsergebnisse sowie deren Umsetzungsmöglichkeiten in der klinischen Praxis da

The Instability Transition for the Restricted 3-Body Problem. III. The Lyapunov Exponent Criterion

We establish a criterion for the stability of planetary orbits in stellar binary systems by using Lyapunov exponents and power spectra for the special case of the circular restricted 3-body problem (CR3BP). The centerpiece of our method is the concept of Lyapunov exponents, which are incorporated into the analysis of orbital stability by integrating the Jacobian of the CR3BP and orthogonalizing the tangent vectors via a well-established algorithm originally developed by Wolf et al. The criterion for orbital stability based on the Lyapunov exponents is independently verified by using power spectra. The obtained results are compared to results presented in the two previous papers of this series. It is shown that the maximum Lyapunov exponent can be used as an indicator for chaotic behaviour of planetary orbits, which is consistent with previous applications of this method, particularly studies for the Solar System. The chaotic behaviour corresponds to either orbital stability or instability, and it depends solely on the mass ratio of the binary components and the initial distance ratio of the planet relative to the stellar separation distance. Our theoretical results allow us to link the study of planetary orbital stability to chaos theory noting that there is a large array of literature on the properties and significance of Lyapunov exponents. Although our results are given for the special case of the CR3BP, we expect that it may be possible to augment the proposed Lyapunov exponent criterion to studies of planets in generalized stellar binary systems, which is strongly motivated by existing observational results as well as results expected from ongoing and future planet search missions.Comment: 10 pages, 8 figures, 3 tables; accepted by Astronomy and Astrophysic

Case Studies of Habitable Trojan Planets in the System of HD 23079

We investigate the possibility of habitable Trojan planets in the HD 23079 star-planet system. This system consists of a solar-type star and a Jupiter-type planet, which orbits the star near the outer edge of the stellar habitable zone in an orbit of low eccentricity. We find that in agreement with previous studies Earth-mass habitable Trojan planets are possible in this system, although the success of staying within the zone of habitability is significantly affected by the orbital parameters of the giant planet and by the initial condition of the theoretical Earth-mass planet. In one of our simulations, the Earth-mass planet is captured by the giant planet and thus becomes a habitable moon.Comment: 24 pages, 8 figures, 3 tables; International Journal of Astrobiology (in press

Measuring the Spin of the Higgs Boson

By studying the threshold dependence of the excitation curve and the angular distribution in Higgs-strahlung at e+e- colliders, e+e- -> HZ, the spin of the Higgs boson in the Standard Model and related extensions can be determined unambiguously in a model-independent way.Comment: 10 pages, 1 Postscript figure, sign typo correcte

Die Behandlungspraxis bei Patienten mit isolierter stumpfer Milzverletzung: Eine Befragung der Schweizer Traumatologen

Zusammenfassung: Hintergrund: Das nicht-operative Management (NOM) des stumpfen Milztraumas hat sich in den vergangenen Jahren als Therapiekonzept etabliert. Es bestehen jedoch zahlreiche Kontroversen bezüglich der Überwachung und Nachsorge dieser Patienten. Ziel dieser Studie war es, mittels einer Umfrage bei Mitgliedern der Schweizerischen Gesellschaft für Allgemeine und Unfallchirurgie (SGAUC) die aktuelle Praxis bezüglich NOM beim isolierten Milztrauma zu erfassen und mögliche Diskrepanzen zur aktuellen Literatur zu eruieren. Studiendesign und Untersuchungsmethode: Sämtliche praktizierende Mitglieder der SGAUC wurden mittels schriftlichem Umfragebogen adressiert. Dieser enthielt Fragen zu Person und Klinik des Chirurgen, Fragen zu Diagnostik und Management während der Hospitalisation sowie zu radiologischen Verlaufskontrollen und zur stufenweisen Wiederaufnahme von Alltagsaktivitäten. Ergebnisse: An der Umfrage nahmen 52 von 165 (31,5%) praktizierenden Mitgliedern der SGAUC teil. Diese deckten 62,8% aller Schweizer Traumazentren ab. Vierzehn Befragte (26,9%) verfügen an ihrer Klinik über ein Protokoll zur Behandlung des Milztraumas. Als initiale Bildgebung beim hämodynamisch stabilen Patienten mit stumpfem Abdomaninaltrauma gaben 82,7% der Befragten die Sonographie an. Bei sonographischem Verdacht auf Milztrauma verzichteten allerdings 19,2% der Befragten auf eine weitergehende Diagnostik. Die Hälfte der Chirurgen gab außerdem an, bei sichtbarem Kontrastmittelextravasat aus der Milz keine weiteren therapeutischen Maßnahmen einzuleiten. 86,5% der Befragten würden Patienten mit niedriggradigem Milztrauma für durchschnittlich 1,6 (0-4Tage) in einem kontinuierlich-monitorisierten Bett überwachen. Keine Unterschiede wurden hinsichtlich der Aktivitätsrestriktion zwischen mittel- und hochgradigen Milztraumata gemacht. Schlussfolgerung: Aufgrund eines Mangels an evidenzbasierten Richtlinien zum NOM des Milztraumas gibt es eine beträchtliche Variabilität in der klinischen Praxis selbst unter erfahrenen Chirurgen. Die größten Diskrepanzen zu den Empfehlungen in der aktuellen Literatur waren zum einen der Verzicht auf eine Computertomographie bei Verdacht auf Milztrauma, zum anderen das konservative Vorgehen trotz nachgewiesenem Kontrastmittelaustrit

Prediction of Post-Weaning Fibrinogen Status during Cardiopulmonary Bypass: An Observational Study in 110 Patients.

BACKGROUND: After cardiac surgery with cardiopulmonary bypass (CPB), acquired coagulopathy often leads to post-CPB bleeding. Though multifactorial in origin, this coagulopathy is often aggravated by deficient fibrinogen levels. OBJECTIVE: To assess whether laboratory and thrombelastometric testing on CPB can predict plasma fibrinogen immediately after CPB weaning. PATIENTS / METHODS: This prospective study in 110 patients undergoing major cardiovascular surgery at risk of post-CPB bleeding compares fibrinogen level (Clauss method) and function (fibrin-specific thrombelastometry) in order to study the predictability of their course early after termination of CPB. Linear regression analysis and receiver operating characteristics were used to determine correlations and predictive accuracy. RESULTS: Quantitative estimation of post-CPB Clauss fibrinogen from on-CPB fibrinogen was feasible with small bias (+0.19 g/l), but with poor precision and a percentage of error >30%. A clinically useful alternative approach was developed by using on-CPB A10 to predict a Clauss fibrinogen range of interest instead of a discrete level. An on-CPB A10 ≤10 mm identified patients with a post-CPB Clauss fibrinogen of ≤1.5 g/l with a sensitivity of 0.99 and a positive predictive value of 0.60; it also identified those without a post-CPB Clauss fibrinogen <2.0 g/l with a specificity of 0.83. CONCLUSIONS: When measured on CPB prior to weaning, a FIBTEM A10 ≤10 mm is an early alert for post-CPB fibrinogen levels below or within the substitution range (1.5-2.0 g/l) recommended in case of post-CPB coagulopathic bleeding. This helps to minimize the delay to data-based hemostatic management after weaning from CPB

The Stability of the Suggested Planet in the nu Octantis System: A Numerical and Statistical Study

We provide a detailed theoretical study aimed at the observational finding about the nu Octantis binary system that indicates the possible existence of a Jupiter-type planet in this system. If a prograde planetary orbit is assumed, it has earlier been argued that the planet, if existing, should be located outside the zone of orbital stability. However, a previous study by Eberle & Cuntz (2010) [ApJ 721, L168] concludes that the planet is most likely stable if assumed to be in a retrograde orbit with respect to the secondary system component. In the present work, we significantly augment this study by taking into account the observationally deduced uncertainty ranges of the orbital parameters for the stellar components and the suggested planet. Furthermore, our study employs additional mathematical methods, which include monitoring the Jacobi constant, the zero velocity function, and the maximum Lyapunov exponent. We again find that the suggested planet is indeed possible if assumed to be in a retrograde orbit, but it is virtually impossible if assumed in a prograde orbit. Its existence is found to be consistent with the deduced system parameters of the binary components and of the suggested planet, including the associated uncertainty bars given by observations.Comment: 11 pages, 10 figures, 3 tables; Monthly Notices of the Royal Astronomical Society (in press

High seroprevalence of human herpes virus 8 (HHV-8) antibodies among vertically HIV-infected pediatric patients living in Germany

Background: Human herpes virus 8 (HHV-8), a gamma herpes virus, is the etiological agent for Kaposi sarcoma (KS). HIV-infected adults with advanced immunodeficiency are at risk. Prevalence data of HHV-8 infection in HIV-infected children living in non-endemic areas are limited. Serologic studies indicate low seroprevalence rates of 3–4% for healthy children living in United States and Germany [1]. Purpose of the study: The aim of the study was to determine the seroprevalence of HHV-8 antibodies among vertically HIV-infected pediatric patients in Germany and to evaluate their association with age, gender, ethnicity, and other demographic factors. Methods: In 2012, a multi-center cross-sectional study was conducted in four University Hospitals in Germany. Stored frozen serum specimens obtained from vertically HIV-infected children and adolescents were tested for antibodies against lytic and latent HHV-8 antigens. Data on patients' demographic characteristics and medical history were recorded. Results: A total of 214 HIV-infected children and adolescents (105 males, 109 females) were included. The median age was 10.2 years (range 1 months–22.6 years). A high proportion of these children (62%) was born in Western Europe, whereas 65% (139/214) of their mothers were born in countries outside Western Europe. The majoritiy (91%) of the children had been treated with highly active antiretroviral therapy and 55.2% (116/210) had a HIV-viral load<50 copies/mL. The median CD4 cell count was 1000/L (range 3–4400). The overall seroprevalence of HHV-8 antibodies was 23.8% (51/214). Seroprevalence rates did not show significant differences between age or gender. In the group of young children aged 1 month to 35 months, 19.4% (46/31) had HHV-8 antibodies, compared to 25% (25/100) in children aged 36 months to 11 years, and 24.1% (20/83) children 12 years and older. In the study group, seroprevalence rates were significantly lower in children who were born in Western Europe (p <0.01) compared to those born in Africa, Asia, or Eastern Europe. Clinical symptoms of HHV-8 infection were reported to be uncommon; only one child had a history of KS at 2 years of age. Conclusions: Vertically HIV-infected pediatric patients living in Germany showed a high HHV-8 seroprevalence of 23.8%. These rates were higher as expected in the normal pediatric population. The findings suggest that HHV-8 infection occurred already in the first years of life

Splice-site mutations cause Rrp6-mediated nuclear retention of the unspliced RNAs and transcriptional down-regulation of the splicing-defective genes

Background: Eukaryotic cells have developed surveillance mechanisms to prevent the expression of aberrant transcripts. An early surveillance checkpoint acts at the transcription site and prevents the release of mRNAs that carry processing defects. The exosome subunit Rrp6 is required for this checkpoint in Saccharomyces cerevisiae, but it is not known whether Rrp6 also plays a role in mRNA surveillance in higher eukaryotes. Methodology/Principal Findings: We have developed an in vivo system to study nuclear mRNA surveillance in Drosophila melanogaster. We have produced S2 cells that express a human b-globin gene with mutated splice sites in intron 2 (mut bglobin). The transcripts encoded by the mut b-globin gene are normally spliced at intron 1 but retain intron 2. The levels of the mut b-globin transcripts are much lower than those of wild type (wt) ß-globin mRNAs transcribed from the same promoter. We have compared the expression of the mut and wt b-globin genes to investigate the mechanisms that downregulate the production of defective mRNAs. Both wt and mut b-globin transcripts are processed at the 39, but the mut bglobin transcripts are less efficiently cleaved than the wt transcripts. Moreover, the mut b-globin transcripts are less efficiently released from the transcription site, as shown by FISH, and this defect is restored by depletion of Rrp6 by RNAi. Furthermore, transcription of the mut b-globin gene is significantly impaired as revealed by ChIP experiments that measure the association of the RNA polymerase II with the transcribed genes. We have also shown that the mut b-globin gene shows reduced levels of H3K4me3. Conclusions/Significance: Our results show that there are at least two surveillance responses that operate cotranscriptionally in insect cells and probably in all metazoans. One response requires Rrp6 and results in the inefficient release of defective mRNAs from the transcription site. The other response acts at the transcription level and reduces the synthesis of the defective transcripts through a mechanism that involves histone modifications